I'd make sure to do a second reboot after the update before you start really using the phone.
When I updated mine, there was the initial reboot done by the update process, after which I saw a "optimizing applications 1 of "XXX" while the phone booted up. After a successful boot, I immediately did a second reboot & got the optimizing notification again, this time for far fewer apps.
Also, give the system a few days to reach normal before you make the call to do a factory reset...